The present invention relates to an asphalt composition which is easily mixed with a styrene-butadiene elastomeric block polymer to form a stable material which is useful for a number of purposes and is particularly useful as a roofing composition. The asphalt composition is a blend of one or more propane extracted petroleum asphalts and a fluid bed catalytic petroleum cracker bottoms oil. It has been found that this particular combination of ingredients of the asphalt blend composition is ideally suited for mixing with styrene-butadiene elastomeric block polymers because said asphalt blend is easily mixed with and forms a relatively stable composition with said elastomers.
It is known in the art that it is desirable to modify asphalt by adding elastomers. However, it is also known, e.g. see U.S. Pat. No. 4,273,685, that it is difficult to form stable compositions of an asphalt and an elastomer. This is particularly true of butadiene-styrene elastomers which are desirably added to asphalt to form, inter alia, roofing compositions as well as paving compositions.
It is also known in the art to add a bottoms oil produced from a fluid bed catalytic petroleum cracker to some types of asphalt for various reasons. See, for example, U.S. Pat. Nos. 4,105,612 and 4,207,117. However, neither of these patents utilize propane extracted asphalts and neither of these patents add the bottoms oil for the purpose of producing an asphalt blend which forms stable compositions with styrene-butadiene elastomers.